The present invention relates generally to object motion recognition. More particularly, the present invention relates to a method of detecting and estimating object motion through a process involving autofocusing subset(s) of complex Synthetic Aperture Radar (“SAR”) images.
SAR autofocus techniques have been designed and used to remove the phase error in the entire image that is still present after reformatting and motion compensation to improve image quality. Two such techniques that correct for cubic and higher ordered errors respectively are (Y. G. Niho “Phase Difference Auto Focusing for Synthetic Aperture Radar Imaging,” U.S. Pat. No. 4,999,635, Filed Mar. 29, 1990, issued Mar. 12, 1991) and (P. H. Eichel, D. C. Ghiglia, and C. V. Jakowatz, “Phase Correction System for Automatic Focusing of Synthetic Aperture Radar,” U.S. Pat. No. 4,924,229, Filed Sep. 14, 1989, issued May 8, 1990).
While the above techniques work for their intended purpose of correcting for the phase error in the overall complex image, i.e., correcting for the phase error that has defocused the entire image, they do not detect or estimate isolated object motion very well.